The invention relates to apparatus and methods for dispensing fluids used in semiconductor processing. More particularly, the invention relates to dispensing developer and rinse solutions onto photosensitive coated substrates with reduced occurrences of defects.
The photolithography process is an important technique used in forming selected circuit patterns on a semiconductor wafer. In general, a photoresist film can be deposited onto a substrate wafer during this process and thereafter pattern-exposed to lithographic equipment in order to transcribe a selected circuit pattern. The photoresist is subsequently developed with a developer solution to obtain a resist pattern corresponding to the transcribed pattern. The developer is intended to remove the relatively more soluble areas of photoresist, and leave behind the remaining patterned image which basically serves as a mask for etching multiple semiconductor wafer layers.
In order to form desired patterns on a substrate, the photoresist is processed during the development step with a solution that is applied in a highly controlled manner. Photoresist or resist development is carried out while a semiconductor wafer is rotated at various speeds and stopped intermittently at preselected time intervals for processing. For example, the wafer may be rotated while a developing solution is dispensed onto the wafer from the discharge port of a developer nozzle. A developing solution film may be thus formed which is intended to have a relatively uniform thickness across the surface of the wafer. Both the wafer and the developer film formed thereon are held stationary thereafter for a predetermined time interval so that developing solution remains in intimate contact with the resist-coated wafer in order to develop a light-exposed latent image thereon. Upon completion of this step in the development process, pure water or other rinse solution can be supplied from a washing liquid supplying nozzle onto the surface of the wafer. The pure water or rinse solution may be eventually scattered off by rotating the wafer at a relatively high speed to spin dry the surface of the wafer to complete this stage of wafer processing.
There are several common methods for developing a photoresist patterned image. For example, multiple wafers may be batched-immersed and agitated in a developer bath during a process known as immersion developing. This development process has certain advantages including high throughput capabilities. However the exposure time of the resist to the developer is relatively long, and the overall process typically does not produce the desired level of tight critical dimension control that is required in processing more densely populated semiconductor wafers. Alternatively, in spray development, the developer can be sprayed onto a resist while the wafer is spun at relatively high speed. Each wafer is individually treated with its own dose of developer solution. While spray development is generally an effective method to dissolve resist, it is often difficult to control the precise and even application of the developer to the wafer through the spray nozzle. During application of the developer, a portion of the solution may be sprayed outside of the wafer surface and wasted. Uneven exposure to developer may also adversely affect critical dimension control.
Another development process followed in the industry today is known as puddle development A predetermined amount of developer is initially dispensed onto the resist surface during this process while the wafer is rotating at a relatively slow speed. The developer can be supplied while the wafer is rotated on a spin chuck and held in place by vacuum suction. As the developer is applied to the wafer, the spinning motion causes the developer to spread out over the surface in a relatively outward direction. Application of the developer is often accomplished through a nozzle that is positioned at a desired location above the wafer which may include a region above its axis of rotation. As the wafer is rotated, the nozzle dispenses developer onto the resist-coated wafer. During application of the developer, it has been observed that the center portion of the wafer is the principal region continuously exposed to freshly dispensed developer. A relatively non-uniform layer of developer may therefore result which can adversely impact critical dimension (CD) control of the patterned resist. Moreover, developer solution is often dispensed rapidly through conventional nozzles such that developer essentially collides with the wafer surface. While it is often desired to coat the entire surface of the wafer with the developer as soon as possible, which calls for the use of a relatively high-pressure supply source, this type of high impact collision with the wafer often leads to adverse consequences such as uneven development of the photoresist pattern or non-uniform line width patterns.
A major problem associated with conventional developing apparatus is their failure to prevent inadvertent dripping of developer onto processed wafer substrates. Following the dispense of developer and rinse solutions with conventional liquid nozzles, residual amounts of fluid are often known to xe2x80x9cdripxe2x80x9d onto the underlying wafer. It is well known that fluid drips are a leading cause of wafer defects. Drips of developing solution or water may also include certain added impurities residing on the surface of a nozzle body which can contaminate the wafer. The occurrence of drips may result in developing defects, line width defects and shape failures along with other undesirable consequences. Moreover, if drops of pure water or other liquid solution inadvertently contact the wafer after substantial completion of the developing process, the undesired effects of what is known as xe2x80x9cpH shockxe2x80x9d can also give rise to wafer defects caused by liquids having a large difference in pH coming in contact with each other. The available equipment and methods used today do not fully meet the high performance demands required by current developer and fluid dispense applications.
There is a need for more improved developer apparatus and methods which reduce the occurrence of wafer defects and uneven development.
The invention herein provides methods and apparatus for controllably dispensing fluids during semiconductor wafer processing. The concepts of the invention may be applied to the develop module within a wafer track system where various developer and rinse solutions can be dispensed onto processed wafers in a highly controlled manner to avoid or minimize wafer defects. All aspects of the invention herein may be applied however to other types of liquid dispense systems or wafer processing modules to reduce the occurrence of unwanted drips onto wafer substrates and coatings. The invention provides flexible methodologies and apparatus that efficiently utilize materials in fluid development and processing: It shall be understood that particular features of the described embodiments of the invention herein may be considered individually or in combination with other variations and aspects of the invention.
It is therefore an object of the invention to provide apparatus for controllably dispensing fluids onto semiconductor wafers. A develop module within a wafer track system may include one or more rotatable liquid dispense arms and dispense nozzles. The fluid dispense apparatus may be specifically selected for developing a photoresist-coated substrate. For example, the develop module may include conventional spin chucks for supporting and rotating the photoresist-coated substrate while exposed to a variety of developer fluids that are dispensed onto the substrate surface. A series of one or more rotatable arms can be mounted adjacent to the spin chuck wherein each supports a dispense nozzle that is connected to developer source(s). The dispense nozzle may be formed with a plurality of nozzle tips for dispensing developer solution onto the photoresist-coated substrate surface. The rotatable arm can be configured to rotate about its longitudinal axis to selectively position the dispense nozzle between various dispense positions which direct the nozzle tips in a direction substantially towards the substrate surface. At the same time, the arm or nozzle itself can be rotated to various non-dispense positions, which direct the nozzle tips substantially away from the substrate surface to reduce risk of dripping developer solution onto the substrate. The rotatable arms herein may include a series of one or more motor-driven actuators for rotating the arm about its longitudinal axis and for sweeping the rotatable arm across selected regions above the substrate. Alternatively the rotatable arm maybe configured as a radial arm which is mounted on a support post to allow pivotal movement about a selected axis to move the nozzle along a predefined arc pathway, or as a linear track arm which moves along a track assembly while supporting the nozzle.
The developer modules and other fluid dispense sections within a wafer track system may further include one or more rotatable rinse arms in accordance with another embodiment of the invention. For selected applications, these arms may be mounted adjacently to the spin chuck for supporting a rinse nozzle that is in fluid communication with rinse source(s). As with the developer nozzles described herein, the rinse nozzle may be similarly formed with a plurality of rinse nozzle tips for dispensing rinse fluid onto a substrate surface. The rinse arm may be also configured to rotate about a longitudinal axis defined along its length in order to selectively position it within preselected ranges of a rinse position and a non-rinse position.
Another aspect of the invention provides methods for developing photoresist-coated semiconductor wafers. The developer and fluid dispense apparatus herein may include a developer arm that is rotatable about its longitudinal axis to selectively rotate the dispense nozzle between a dispense position and a non-dispense position. While in the dispense position, the arm or nozzle itself can be rotated so as to direct the nozzle tips towards the wafer surface which facilitates fluid dispense onto the surface. While in the non-dispense position, the arm or nozzle can be rotated to direct the nozzle tips away from the wafer surface to reduce the likelihood of any undesired drips falling thereon. The nozzle tips through which fluid is dispensed may be thus pointed within a full range of directions including: a relatively neutral or upwardly pointing direction relative to the wafer surface to minimize drips; and a relatively downwardly pointing direction relative to the wafer surface while dispensing developer or other fluids.
Other goals and advantages of the invention will be further appreciated and understood when considered in conjunction with the following description and the accompanying drawings. While the following description may contain specific details describing particular embodiments of the invention, this should not be construed as limitations to the scope of the invention but rather as an exemplification of preferable embodiments. For each aspect of the invention, many variations are possible as suggested herein that are known to those of ordinary skill in the art. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof.